The present invention relates to an exhalation system for use with ventilators, particularly adult volume ventilators used to control and assist a patient's breathing.
Ventilator breathing systems for assisting respiration of patients who are unable to breathe adequately on their own normally include an inhalation hose through which a controlled mixture of gas from the ventilator is inhaled by the patient, and an exhalation assembly through which gas is exhaled. The exhalation assembly normally includes an exhalation valve for shutting off the outlet path while the patient is inhaling, and a flow meter or other monitoring device such as bellows-type spirometer for monitoring the patient's exhaled tidal volume.
One problem in such breathing systems is in keeping the exhalation components clean, dry and sterile. Exhaled air will contain moisture which tends to cool and condense in the exhalation components, adding to the contamination problem.
Another problem is the risk of contamination of the surrounding air by exhalation of bacteria-laden air from an ill patient. The risk of air-borne or contact cross infection is reduced by incorporation of a bacteria filter in the exhalation path, but this adds another component requiring frequent cleaning and sterilization.
In previous ventilator exhalation systems it has been necessary to disassemble, clean and sterilize the exhalation components on a fairly frequent basis. Some of the components, for example bellows-type spirometers, will collect moisture and are extremely difficult to clean and sterilize. When this must be done on a daily basis, or more frequently in some cases, considerable staff time and costs are involved. Additionally, frequent cleaning and sterilization reduces the component lifetime so that they require more frequent replacement, which also adds significantly to the cost.
In some prior systems the bacteria filter has been heated in an attempt to avoid or reduce condensation in this component. Although this can reduce the build-up of contamination in the filter itself, condensation and contamination in the downstream components such as the spirometer are still a problem.